Automotive safety has been a major concern in the automotive industry for decades, and will continue to be so. Many safety features have been developed to reduce the impact loads on the passengers sitting within the vehicle. For example, exterior parts on vehicles such as bumpers and energy absorbing panels help reduce and distribute impact loads. Crushable impact zones are where sheet metal structures bend and deform thereby absorbing energy in the process. Seat belts have been developed to hold the passenger within the seat and prevent the passenger from impacting the inside cabin of the vehicle. In recent times, airbags have become standard on most vehicles sold. Airbags automatically and instantaneously inflate during an impact such that it provides a cushion between the passenger and the interior of the cabin. Airbags originally were designed to inflate from the steering wheel protecting just the driver. Now airbags are inflated from the side windows, in front of the passenger seat, and even about the knees. Other safety measures are not so obvious. For instance, much of the interior of the vehicle can be padded with foams or soft plastics. Sometimes an aesthetically pleasing surface of an interior panel is backed by energy absorbing foam. Collapsible steering columns prevent the steering column from penetrating into the cabin and causing further injury. Glass is no longer a single piece, but rather two glass or plastic sections sandwiched about a common plastic liner. Upon impact the plastic liner gives while retaining the shards of glass from becoming dangerous projectiles. Overall, safety is a major concern in the automotive industry.
Generally speaking, safety measures can be divided into either active safety devices or passive safety devices. Because no action by the vehicle occupant is required to activate or use an airbag, it is considered a passive safety device. This is in contrast to seat belts, which are considered active safety devices because typically the vehicle occupant must act to enable them. Terminological confusion can arise from the fact that passive safety devices and systems, those requiring no input or action by the vehicle occupant, can themselves operate in an active manner; an airbag is one such device. Vehicle safety professionals are generally careful in their use of language to avoid this sort of confusion, though advertising principles sometimes prevent such syntactic caution in the consumer marketing of safety features. Nonetheless, it is desired when designing a new safety feature that it is to be passive. This prevents the driver or passengers from failing to activate a particular safety device.
Airbags and airbag system design have evolved significantly over the many years since their introduction to motor vehicles. In the beginning stages of airbag development, controlling the rapid inflation of the cloth bag itself was quite challenging. The airbag was designed for the 95 percentile human being, and many times the mere inflation of the airbag striking a child or a person of small size was a real danger. Sensors in the seat can weigh the occupant and determine whether inflation of the airbag would be beneficial or detrimental. Finding a perfect choice of the airbag material itself was quite challenging. Despite various considerations of material options for the cushion material, nylon 6-6 remains the material of choice. While airbags are meant to protect the occupants, it is extremely challenging to design them to be perfect.
For airbags to perform their protective function, each component within the system must demonstrate reliability and predictability. The key function of the airbag cushion is to contain a hot and high pressure gas mixture allowing a safe and efficient deceleration of the vehicle occupant during the rapid deceleration of the vehicle in a collision. Elastic fiber deformation and controlled hot gas flow through the fabric controlled by the structural elements of the cushion, such as the seam or vents, are the principal mechanisms that provide this function. In addition to the demanding functionality, the systems are constrained further as the airbag cushions are designed to be stored in steering wheels, under instrument panels or inside the roof rails with replacement periods of up to 15 years.
In spite of severe design challenges, the bottom line is that airbags save lives. The US National Highway Transportation Safety Authority (NHTSA) and Insurance Institute for Highway Safety (IIHS) have been collecting data comparing airbag and non-airbag equipped vehicles involved in traffic incidents for a number of years. These data have demonstrated that almost 10,000 potential fatalities have been prevented in the US alone since 1985. The number of lives saved has increased year by year as the fitment of first driver, then passenger and now head and side airbags has risen. Aside from saving lives, the airbag has also led to a new market in automotive safety representing $4 billion annually with continued double-digit annual growth expected through the next decade. Significant future growth in airbag usage will come from a number of areas. Side impact and rollover protection are increasing in importance in North America. The Asia Pacific market is expanding rapidly in China and Korea, while side impact protection continues to increase in importance in japan. In Europe there is clear evidence that enhanced safety sells automobiles, and even mid-range priced automobiles can be equipped with nine airbags as standard. There is also survey evidence supporting this fact on a more global level, with a number of consumer reviews ranking safety above price, performance and fuel economy as the most important consideration of car buyers.
The evolution in demand for airbag systems has been accompanied by significant technical development. The key driver for this development is maximizing the protection of vehicle occupants and thus reducing potential risk of injury. The global influencing factor in the foreground of these developments has been competitive pressure to enhance vehicle safety as measured in crash test series such as the NHTSA New Car Assessment Program NCAP, and the European equivalent EuroNCAP. Locally, in North America, changes in the Federal Motor Vehicle Safety Standard have mandated improvements, while changes in product liability legislation in North America and Europe have driven manufacturers into more cautious behavior in relation to systems design and materials specification.
Many considerations must be taken into account when designing safer vehicles. One design strategy is to the make the vehicle larger and heavier and therefore decreases the chance of it collapsing to some extent during an impact. However, heavier vehicles are more dangerous to other vehicles that aren't as heavy. Furthermore, heavier vehicles require more fuel to travel the same distance. In today's desire of ultra-efficiency fuel mileage, weight and safety considerations are hard to reconcile.
Accordingly, there is a need for an additional safety device that is passive, in that it doesn't require the occupants to activate it. Also, there is a need for the additional safety device to be light in terms of weight, such that it doesn't negatively affect fuel consumption or the design of the vehicle. Furthermore, there is a need for the additional safety device to be simple in operation and not have its own negative side effects or problems. The present invention fulfills these needs and provides other related advantages.